Piston with head insert and process of making it



Dec. 25, 1956 w, 3, CHENEY 2,775,493

PISTON WITH HEAD INSERT AND PROCESS OF MAKING IT Filed Nov. 27, 1955 2/ 5 INVENTOR. IVE'NDELL CHE/v5);

I 1' 22 Y ATTORNEYS.

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PISTON WITH HEAD INSERT AND PROCESS OF MAKING IT Application November 27, 1953, Serial No. 394,696

11 Claims. (Cl. 309-9) In the manufacture of pistons for internal combustion engines, the use of light metals such as aluminum or aluminum alloys has become very general. Light metal pistons have many advantages which are well known in the art. In diesel engines and similar internal combustion devices, fuel is injected into the cylinders in the form of a jet which normally impinges on the tops of the pistons. The heat generated by the fuel injection jet on a local area of the piston head is very high; and it has been found that aluminum and its alloys may exhibit local impairment under such operating conditions.

It is an object of my invention to provide a piston which is protected against such impairment, pitting erosion and failure due to the high heats of fuelinjection jets, and to provide an inexpensive, convenient and satisfactory mode of making such pistons.

More. specifically, it is an object of the inventionto provide a light metal piston having a heat and erosion resistant iinserttin the head thereof for the purpose set forth, and a method of manufacturing pistons with a bonded head insert.

These and other objects of my invention, which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that construction and arrangement of parts and in those procedures of which I shall now describe exemplary embodiments. Reference is made to the drawings forminga part herein, and wherein:

Fig. 1 is a top plan view of a piston having a head insert and made in accordance with my invention.

Fig. 2 is a partial vertical sectional view thereof taken along the section line 2-2 of Fig. 1.. s a

Fig. 3 is a partial verticalsectional View thereof taken along the section line 3-3 of Fig. 2.

Fig. 4 is a top plan view of one form of head insert which I may use.

Fig. 5 is a vertical sectional view thereof taken along the section line 55 of Fig. 4.

Fig. 6 is a bottom plan view of the exemplary insert member.

Fig. 7 is a partial vertical sectional view of a piston showing another form of insert.

Briefly, in the practice of my invention, I form a piston of light metal by casting in a mold of. suitable configura- Since the eifect of the excessive heats generated by the fuel injection jets is a localized one, it is sufiicient to incorporate in the piston head an insert member of heat and erosion resistant character which is smaller than the piston head in horizontal area and is positioned so as to protect thatpart of the piston head on which the jet would otherwise impinge. Stated in a different fashion, my invention contemplates the association with the light metal piston head of an insert member of relatively small'mass as compared with the piston, so located as to protect the piston head, having the property of assisting in the dissipation of heat, and the property of resisting pitting and erosion from the jet, and preferably having a non-symmetrical shape with rounded edges. 1 In United States Patent 0 2,775,493 latented Dec. 25, 1956 an exemplary embodiment, the insert will be exposed above the piston head, and so positioned as to receive the impact of the jet, and will be of sufficient size to break up the jet and dissipate its direct force before any part of the injected material reaches the light metal portion of the piston. Since the position of the jet forming means as well as the force of the injection jet will vary in different engines, it will be understood that variations may be made by the skilled worker in the size, shape and in the placement of the insert.

I shall now describe a preferred type of insert in an exemplary embodiment of the invention. This insert has a portion, as hereinafter explained, which, rising above the top surface of the light metal portion of the piston, can be located in a corresponding recess in the mold in which the piston is to be cast. This not only serves as a means for positively locating the insert in the piston head, but also permits the top or impact receiving surface of the insert to be located substantially above the contiguous top portions of the piston body. The remaining portion or portions of the insert are designed to be embedded in the top of the piston as an incident of the cast light metal body of the piston itself.

This insert does not extend through the top portion of the piston so that no problem of gaseous leakage through the piston head is involved even. though there should be a failure of the bond between the insert and the piston body.

The term light metal as used herein is intended to be inclusive of aluminum and alloys of aluminum with other metals,.including but without limitation silicon, magnesium, and the like. There are many alloys of aluminum which are suitable for the manufacture of pistons for internal combustion engines, so that the specific nature of the light metal does not form a limitation on the present invention. By way of example, I may employ an alloy available under the trade name of Vanasil which contains from 21% to 23% of silicon together with small amounts of nickel, copper, vanadium and magnesium.

The specific material of the insert is likewise not a limitation on the invention. A ferrous material, or indeed, any other metallic material which possesses the required heat resisting and other qualities, may be used. Excellent materials are wrought iron, all of the many and varied varieties of stainless steels, and alloy cast iron.

Referring to Figs. 1, 2 and 3, a cast piston body is indicated at 6 having a head portion 7. In high compression engines the head usually has a concavity indicated at 8, although it may be otherwise formed. An insert has been shown at 9 having a portion extending above the surface of the top of the piston and another portion which is embedded in the substance of the piston head. As has been indicated above, the exact position of the insert on the piston head can be varied depending upon the position of the jet forming means in the cylinder in which the piston is to be used. Ordinarily, the jet forming means will be off center with respect to the cylinder cross-section, so thatit will be usual to locate my insert in an eccentric position. Where the insert in its desired position intersects the axis of the piston, it will usually be found a matter of convenience to provide the insert with a bottomed center hole l0 which can be employed not on'ly'in locating the insert in a mold, but also later 3 to receive a lathe center in turning the outside, cylindrical portion of the piston and in forming therein the ring grooves 12.

Reference is next made to Figs. 4, 5 and 6. The exemplary insert presents a top surface 13 to receive the impact of the jet. This surface will be normally planar, but it may have such other configuration as is deemed desirable. Adjacent the top surface 13 I have shown what is essentially a cylindrical portion 14. The cylindrical portion terminates downwardly in a flaring or relatively sharply demarked portion 15. This portion may have various configurations, but it should extend outwardly from the cylindrical portion 14. The cylindrical portion is designed to be inserted in a recess in a mold so that the mold positions the insert during the casting of the piston. It will be understood that where the top of the piston is characterized by the concavity 8 or other non-planar configuration, the recess in the mold may be required to encompass some portion of the fiaring part 15. The recess may also be provided with a pin to enter the center hole 10 and assist in the location of the insert.

The portion 14 could have a peripheral configuration other than circular, as for example, oval, polygonal, or even irregular; but a circular or cylindrical configuration is easiest and cheapest to produce not only on the insert but also by way of the recess in the mold.

Beyond the flaring portion 15, I preferably form a laterally projecting skirt 16 for additional anchorage. On the under side the insert is preferably cut back for about the thickness of the skirt centrally as at 17, the skirt also beingcut through at opposite sides, as at 18 and 19. Thus, a configuration is provided which not only gives excellent anchorage to the insert but prevents any rotative displacement thereof. It is preferable to round all edges, corners or meeting lines between angularly related portions in any part of the insert which is to be embedded in the piston head. This is clearly shown in the drawm-gs.

The insert, as a structure, is one easily formed by casting, forging or like operations. It may, of course, be machined from a larger piece of metal, although this is more expensive. Where metal molds are to be used for casting the pistons, it may be found advantageous to machine or grind the portion 14 which is to be engaged in the mold recess. When the insert has been properly positioned in the mold, the casting of the piston will ensue. Needless to say, the insert will preferably be cleaned mechanically or chemically before being positioned in the mold.

While I have herein described a structure including an insert having a portion projecting from the top of the piston and another portion embedded in the light metal casting, I am not so limited, nor am I limited to the specific shape shown for the insert. Any non-symmetrical shape with well-rounded edges suitable for embedding in a casting will serve the purpose. An advantage of the type of insert in which a portion projects, as shown in Figs. 1, 2 and 3, is that the projecting portion may be used to position the insert in the mold. But it is readily possible to provide an insert which does not project from the top of the piston. In Fig. 7 I have shown the cast metal piston body 6 as provided with an insert element 20, the top surface of which is flush with the top surface of the piston, as at 21. Here a different mode of supporting the insert during the casting has been indicated as comprising wire chaplet members 22 adapted to be engaged with the mold core. Indeed, if the surface of the metallic insert terminated, say, at the dotted line 23 in Fig. 7, it would be possible entirely to embed the insert in the cast structure forming the top of the piston. Here, while there would clearly be a relatively thin layer of the light metal overlying the insert, it maybe pointed out that the insert would still protect the structure. Abrasion, pitting, and heat deterioration of the overlying layer of light metal would not only be inhibited when the underlying insert is reached, but also the overlying light metal would, to a large extent, be protected from these influences by a rapid dissemination of heat produced by the insert. Nor am I limited to cast, wrought, or machined structures for the insert since, in some instances, relatively heavy metal stampings will serve.

Various procedures may be employed to form a bond between embedded portions of the insert and the light metal of the piston body. Thus, I may follow procedures outlined in the copending application of Marshall G. Whitfield, entitled Casting Light Metal Against Iron, and Article Formed Thereby, Serial No. 309,773, filed September 16, 1952. These procedures involve, among other things, casting the piston in such fashion that there is a substantial flushing of the surfaces of the insert by molten metal flowing past them before the molten light metal is allowed to become quiescent and to solidify. The surface of the insert may be coated electrolytically or otherwise with an adhesion promoting metal such as tin or zinc, and the light metal cast thereagainst. Again, the surface of the insert may be coated with molybdenum, and if desired, the insert may then be dipped in molten aluminum to form a coating thereon before the light metal is cast against the insert.

Modifications may be made in my invention without departing from the spirit of it. Having thus described my invention in certain exemplary embodiments, what I claim as new and desire to secure by Letters Patent is:

l. A cast, light metal piston having in the head thereof a heavy metal insert of greater breadth than depth, said insert being embedded in the head portion of the piston in light metal cast around it to form the piston, said insert having a top portion and a base portion, the said top portion having at least a top surface exposed at the top surface of the piston and so positioned as to protect the piston from deterioration due to high velocity jet impact when the piston is employed in a diesel-type internal combustion engine, said insert also having a bottom portion of greater external dimensions than the top portion and wholly embedded in the light metal of the piston so that removal of the said insert is prevented by portions of the said light metal overlying said base portion.

2. The structure claimed in claim 1 wherein the said metal insert has an irregular shape suitable for anchoring in the cast metal,.and is made from material chosen from a class consisting of wrought iron, stainless steel, and alloy cast iron.

3. The structure claimed in claim 1 in which the top portion of the said insert is substantially cylindrical in conformation and extends above the top surface of the said piston sutficiently to permit the casting of the piston to be done around the base of the insert while the said top portion of the insert is engaged in an orifice in a mold whereby the said insert is supported during casting.

4. The structure claimed in claim 1 wherein the base portion of the said insert is grooved beneath to prevent rotative movement of the said insert.

5. The structure claimed in claim 4 wherein the said insert is located eccentrically in the top of the said piston but embraces the longitudinal axis thereof, and wherein the said insert is provided with a center hole in the said axis.

6. The structure claimed in claim 1 wherein the embedded portions of the said insert are metallurgically bonded to the body of the said light metal piston.

7. A process of producing a cast light metal piston with a head insert which comprises providing a ferrous insert member having a projecting portion and an anchoring portion of larger external dimensions, locating the said insert in a mold for a piston with said projecting portion engaging in a recess in said mold, and casting light metal in said mold to form a piston in which said anchoring portion of said insert is embedded in the top portion of said piston and extends only partially through.

8. The process claimed in claim 7 including the step of interposing a layer of adhesion-promoting metal between the anchoring portion of said insert and the cast light metal.

9. A ferrous insert for the purpose described having a body comprising an extending portion and an anchoring portion, said extending portion having acontour adapted for insertion in a mold recess to support it during casting, and said anchoring portion having an effectively larger contour for embedding in a mass of cast metal.

' 10. The structure claimed in claim 9 wherein said projecting portion has a substantially cylindrical shape and wherein said anchoring portion is characterized by a laterally extending skirt with rounded edges.

11. The structure claimed in claim 9 wherein said projecting portion has a substantially cylindrical shape and wherein said anchoring portion is characterized by a laterally extending skirt with rounded edges and wherein the said skirt is characterized by a laterally extending groove to prevent rotation of the said insert.

References Cited in the file of this patent UNITED STATES PATENTS France Oct. 18, 1951 

